The invention relates to a method and a device for producing molded trim parts. Such molded trim parts may be used, for example, for the interior lining of passenger compartments in a motor vehicle or for the visual design of domestic appliances. Such a molded trim part includes a layer of a decorative material (for example wood veneer, textile, leather), which enhances the visual appearance of the trim part. The decorative material is usually flexible and/or sensitive to mechanical damage. Therefore, to produce a molded trim part, the decorative material is usually back-molded on one side with a backing material (for example synthetic resin), which has the required mechanical stability. On the side facing away from the molded-on backing material, the decorative material is usually coated or overmolded with a protective material. The protective material is in this case usually transparent and forms surfaces of good visual quality (for example plastics from the group of polyurethanes (PUR) or polymethylmethacrylate (PMMA)). The molded trim parts concerned here are accordingly composite materials that usually have three layers (backing material, decorative material, protective material).
To produce molded trim parts, usually a blank is first preformed from a decorative material in a compression mold. After that, the preform is transferred into an injection-molding device and back-molded there with a backing material. In a next step, the workpiece is transferred into a second injection-molding device and overmolded there with a protective material. Finally, there then follows a trimming operation, in order to cut the molded trim part to a final size. In particular, this necessarily involves reworking the border of the workpiece that is held during the back-molding and overmolding operations. Such a method can be carried out on a production line in continuous operation and is therefore suitable for the mass production of molded trim parts. However, between the work steps, the respective intermediate product is changed over to a next tool. This has the disadvantage that sensitive surfaces may be damaged or the preformed parts may be distorted; the latter results if different method steps are carried out at greatly varying temperatures. This may negatively impact the quality and create dimensional inaccuracies.
EP 1 629 956 A1 describes a method and a device for producing trim parts such that, all the method steps (molding, overmolding, back-molding, cutting to size) are performed in one working device. This avoids losses in quality that are caused by intermediate products being changed over into different devices. However, the method is exclusively sequential, that is to say can only be carried out for one workpiece at a time. The working device is unavailable until a trim part is completely finished. This leads to unused waiting times during the respective method steps, which has adverse effects on the cost-effectiveness of the method.